In oil and gas exploration, the problem of locating a cable behind casing requires careful consideration. In new oil and gas well development, in many cases, a fiber optic cable is placed behind the casing for sensing or communication purposes. At the same time, however, the cable has to be protected from the damaging effects of perforation charges. Normally, the perforation would be placed at a convenient angular location to minimize the possibility of damaging the fiber cable.
To make the cable more detectable, it is normally surrounded or attached to ferromagnetic steel that can be detected by eddy currents which are induced in the metal when a solenoid transmitter passes nearby. The location of the cable can then be determined by detecting the induced eddy currents. The angular position of the cable is then determined at every depth along the casing. Once the cable angular position is determined, the orientation of the perforations can be chosen to minimize the risk of damage to the cable.
The problem with the conventional detection approach is the time required to locate the cable. The conventional approach requires stationary measurement at a number of angles, at every depth, in order to find the cable position. This is time consuming, thus greatly increasing completion time and cost.